Fig. 1. Percentages of patients according to the epiduroscopic findings among the three groups. The size of the pneumatic space after injecting air was smaller (P = 0.0347) and the density of vascular network (P = 0.0001) was greater in the third-trimester group than in the other two groups. The amount of the engorged blood vessels was greater in the first and third-trimester groups than in the nonpregnant group (P = 0.0001). The water content in the connective tissue was greater in the third-trimester group than in the nonpregnant group (P = 0.0237). Stippled bars = score 1 (narrow or none or extremely little); hatched bars = score 2 (patent or moderate); cross-hatched bars = score 3 (widely patent or considerable).